title: BRAFV600E immunohistochemistry facilitates universal screening of colorectal cancers for Lynch syndrome.
abstract: BRAFV600E mutation in microsatellite-unstable (MSI) colorectal carcinomas (CRCs) virtually excludes Lynch syndrome (LS). In microsatellite-stable (MSS) CRCs it predicts poor prognosis. We propose a universal CRC LS screening algorithm using concurrent reflex immunohistochemistry (IHC) for BRAFV600E and mismatch-repair (MMR) proteins. We compared BRAFV600E IHC with multiplex polymerase chain reaction (PCR) and matrix-assisted laser desorption/ionization-time of flight mass spectrometry in 216 consecutive CRCs from 2011. Discordant cases were resolved with real-time PCR. BRAFV600E IHC was performed on 51 CRCs from the Australasian Colorectal Cancer Family Registry (ACCFR), which were fully characterized for BRAF mutation by allele-specific PCR, MMR status (MMR IHC and MSI), MLH1 promoter methylation, and germline MLH1 mutation. We then assessed MMR and BRAFV600E IHC on 1403 consecutive CRCs. By matrix-assisted laser desorption/ionization-time of flight mass spectrometry 15 cases did not yield a BRAF result, whereas 38/201 (19%) were positive. By IHC 45/216 (20%) were positive. Of the 7 discordant cases, real-time PCR confirmed the IHC result in 6. In the 51 CRCs from the ACCFR, IHC was concordant with allele-specific PCR in 50 cases. BRAFV600E and MSI IHC on 1403 CRCs demonstrated the following phenotypes: BRAF/MSS (1029 cases, 73%), BRAF/MSS (98, 7%), BRAF/MSI (183, 13%), and BRAF/MSI (93, 7%). All 11/1403 cancers associated with proven LS were BRAF/MSI. We conclude that BRAF IHC is highly concordant with 2 commonly used PCR-based BRAFV600E assays; it performed well in identifying MLH1 mutation carriers from the ACCFR and identified all cases of proven LS among the 1403 CRCs. Reflex BRAFV600E and MMR IHC are simple cheap tests that facilitate universal LS screening and identify the poor prognosis of the BRAFV600E-mutant MSS CRC phenotype.
authors.affiliation: *Department of Anatomical Pathology †Northern Cancer Translational Research Unit ††Familial Cancer Clinic, Royal North Shore Hospital ∥Department of Pathology, SYDPATH, St Vincents Hospital, Darlinghurst ¶Faculty of Medicine, University of NSW ¶¶Sydney Medical School, University of Sydney, Sydney, NSW §§Department of Molecular and Cellular Pathology ‡Department of Pathology, School of Medicine, University of Queensland ‡‡Envoi Specialist Pathologists, Herston §Cancer and Population Studies Group, Queensland Institute of Medical Research, Brisbane, QLD ∥∥Centre for Molecular, Environmental, Genetic and Analytic Epidemiology, School of Population Health, University of Melbourne, Carlton, Vic., Australia #Department of Neuropathology, Institute of Pathology, Ruprecht-Karls University **Clinical Cooperation Unit Neuropathology, German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Toon
authors.forename: Michael D
authors.initials: MD
authors.lastname: Walsh
authors.forename: Angela
authors.initials: A
authors.lastname: Chou
authors.forename: David
authors.initials: D
authors.lastname: Capper
authors.forename: Adele
authors.initials: A
authors.lastname: Clarkson
authors.forename: Loretta
authors.initials: L
authors.lastname: Sioson
authors.forename: Stephen
authors.initials: S
authors.lastname: Clarke
authors.forename: Scott
authors.initials: S
authors.lastname: Mead
authors.forename: Rhiannon J
authors.initials: RJ
authors.lastname: Walters
authors.forename: Mark
authors.initials: M
authors.lastname: Clendenning
authors.forename: Christophe
authors.initials: C
authors.lastname: Rosty
authors.forename: Joanne P
authors.initials: JP
authors.lastname: Young
authors.forename: Aung Ko
authors.initials: AK
authors.lastname: Win
authors.forename: John L
authors.initials: JL
authors.lastname: Hopper
authors.forename: Ashley
authors.initials: A
authors.lastname: Crook
authors.forename: Andreas
authors.initials: A
authors.lastname: von Deimling
authors.forename: Mark A
authors.initials: MA
authors.lastname: Jenkins
authors.forename: Daniel D
authors.initials: DD
authors.lastname: Buchanan
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Gill
mesh_terms: D000465:Algorithms; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000175:diagnosis* / Q000235:genetics* / Q000378:metabolism; D053843:DNA Mismatch Repair; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008403:Mass Screening / Q000379:methods*; D053842:Microsatellite Instability; D060885:Multiplex Polymerase Chain Reaction; D009154:Mutation; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D046888:Tissue Array Analysis
chemical_list: C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf